Before the patch this was a problem, after the patch it seems to have gotten worse.
Shoot an NPC ship to bare numbers: sails < 65%, crew < 10, hull < 50% and that ship can still turn fast through the wind out run me and has become nearly impossible to board.
Last night, I was in a battle with a trader snow, had their sails down to 63%, hull was probably about 30%, crew was 2 and that ship was flying around as if it were 150% manned. Before the patch it would take me 30 to 40 minutes of careful chain shots and grape to get the ship to boarding stage. Last night I almost ran out the 1.5 hour battle timer and still couldn't board.
NPC's need to be more realistic AND surrender.